Practice Questions

<ul style="color: rgb(255,255,255);"><li>Salinity Definition: Salinity refers to the total amount of solid material dissolved in seawater. It is typically expressed in parts per thousand (ppt or ‰).</li><li>Average Value: The average salinity of the world's oceans is consistently accepted as 35 parts per thousand (35‰), meaning there are 35 grams of dissolved salts in 1,000 grams of seawater.</li><li>Primary Composition: Sodium Chloride (NaCl), or common table salt, is the most abundant salt in seawater, accounting for about 77.8% of the total dissolved salts. Other major ions include magnesium, sulfate, calcium, and potassium.</li><li>Factors Influencing Salinity:<ul style="color: rgb(255,255,255);"><li>Evaporation: Higher rates of evaporation increase salinity (e.g., in the Red Sea).</li><li>Precipitation/Freshwater Input: High rainfall, river discharge, or melting glaciers decrease salinity (e.g., near the mouths of large rivers like the Amazon).</li><li>Temperature: Higher temperatures usually correlate with increased evaporation, raising surface salinity levels.</li></ul></li><li>Regional Variation: While the global average is 35‰, salinity varies by latitude:<ul style="color: rgb(255,255,255);"><li>Equator: Salinity is lower due to heavy rainfall and cloud cover reducing evaporation.</li><li>Subtropics (20°-30° latitudes): Salinity is generally highest due to high evaporation rates and low precipitation.</li><li>Polar Regions: Salinity is lowest due to the freezing of water (which excludes salt) and the melting of sea ice (which dilutes water).</li></ul></li><li>Measuring Unit: Historically measured in ppt, modern oceanography also utilizes the Practical Salinity Scale (PSS), which is based on the electrical conductivity of seawater and is dimensionless.</li></ul>

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